I'm guessing that some of us are missing some very useful fonts. As a multi-lingual kind of place, we all need to have a selection of fonts that allow us to see all the unicode goodness that documents might offer. Here's my list of good-to-have fonts:

DejaVu: http://dejavu.sourceforge.net/
Gentium: http://www.sil.org/~gaultney/gentium/
Aboriginal Sans/Serif: http://www.languagegeek.com/font/fontdownload.html
Thryomanes v1.2: http://www.io.com/~hmiller/lang/

Yes, there are others, but these will cover basic requirements. To stay up-to-date, you should get them from the above sites but to be neighbourly I've uploaded a zip file containing these fonts. Get it here.